docs: named lifetimes

* Include tip given by Leo Testard in mailing list about labeled `break`
and `continue`:
https://mail.mozilla.org/pipermail/rust-dev/2014-March/009145.html
* cross-reference named lifetimes in tutorial -> lifetimes guide
* Broke named lifetimes section into two sub-sections.
* Added mention of `'static` lifetime.
Added suggested notes

* Note on while loop not supporting named breaks.
* Note on hygienic macros (and example of such within loops)
green: Remove the dependence on the crate map

This is the final nail in the coffin for the crate map. The `start` function for
libgreen now has a new added parameter which is the event loop factory instead
of inferring it from the crate map. The two current valid values for this
parameter are `green::basic::event_loop` and `rustuv::event_loop`.
rustc: Remove all crate map support

The crate map is no longer necessary now that logging and event loop factories
have been moved out.

Closes #11617
Closes #11731
doc: Update the runtime guide with green changes

This updates a few code examples about booting libgreen/libnative and also
spells out how the event loop factory is required.
Prefer lifetime suggestion over generic error
rustuv: Handle short writes in uv_fs_write

The libuv fs wrappers are very thin wrappers around the syscalls they correspond
to, and a notable worrisome case is the write syscall. This syscall is not
guaranteed to write the entire buffer provided, so we may have to continue
calling uv_fs_write if a short write occurs.

Closes #13130
std: Explicitly link to libm for freebsd

Apparently we had forgotten to do this for freebsd, causing possible problems
on FreeBSD 10. The discussion in #12324 has some more details about how it's
missing.
libstd: Document the following modules:

* native::io
* std::char
* std::fmt
* std::fmt::parse
* std::io
* std::io::extensions
* std::io::net::ip
* std::io::net::udp
* std::io::net::unix
* std::io::pipe
* std::num
* std::num::f32
* std::num::f64
* std::num::strconv
* std::os
std: Touch various I/O documentation blocks

These are mostly touchups from the previous commit.
Changed `iter::Extendable` and `iter::FromIterator` to take a `Iterator` by value
auto merge of #13106 : CLUSTERfoo/rust/docs/labelled_breaks, r=brson

* Include tip given by Leo Testard in mailing list about labeled `break`
and `continue`:
https://mail.mozilla.org/pipermail/rust-dev/2014-March/009145.html
* cross-reference named lifetimes in tutorial -> lifetimes guide
* Broke named lifetimes section into two sub-sections.
* Added mention of `'static` lifetime.
auto merge of #13039 : Kimundi/rust/iter_by_value_extend, r=alexcrichton

# Summary 
Changed `iter::Extendable` and `iter::FromIterator` to take a `Iterator` by value.
These functions always exhaust the passed `Iterator`, and are often used for transferring the values of a new `Iterator` directly into a data structure, so using them usually require the use of the `&mut` operator:

```
foo.extend(&mut bar.move_iter()); // Transfer content from bar into foo

let mut iter = ...;
foo.extend(&mut iter); // iter is now empty
```
This patch changes both the `FromIterator` and `Extendable` traits to take the iterator by value instead, which makes the common case of using these traits less heavy:

```
foo.extend(bar.move_iter()); // Transfer content from bar into foo

let iter = ...;
foo.extend(iter);
// iter is now inaccessible if it moved
// or unchanged if it was Pod and copied.
```
# Composability
This technically makes the traits less flexible from a type system pov, because they now require ownership. 

However, because `Iterator` provides the `ByRef` adapter, there is no loss of functionality:
```
foo.extend(iter.by_ref()); // Same semantic as today, for the few situations where you need it.
```

# Motivation
This change makes it less painful to use iterators for shuffling values around between collections, which makes it more acceptable to always use them for this, enabling more flexibility.

For example, `foo.extend(bar.move_iter())` can generally be the fastest way to append an collections content to another one, without both needing to have the same type. Making this easy to use would allow the removal of special cased methods like `push_all()` on vectors. (See https://github.com/mozilla/rust/issues/12456)

I opened https://github.com/mozilla/rust/issues/13038 as well, to discuss this change in general if people object to it.

# Further work
This didn't change the `collect()` method to take by value `self`, nor any of the other adapters that also exhaust their iterator argument. For consistency this should probably happen in the long term, but for now this is too much trouble, as every use of them would need to be checked for accidentally changed semantic by going `&mut self -> self`. (which allows for the possibility that a `Pod` iterator got copied instead of exhausted without generating a type error by the change)
auto merge of #13117 : alexcrichton/rust/no-crate-map, r=brson

This can be done now that logging has been moved out and libnative is the default (not libgreen)
auto merge of #13133 : alexcrichton/rust/issue-13130, r=brson

The libuv fs wrappers are very thin wrappers around the syscalls they correspond
to, and a notable worrisome case is the write syscall. This syscall is not
guaranteed to write the entire buffer provided, so we may have to continue
calling uv_fs_write if a short write occurs.

Closes #13130
auto merge of #13134 : alexcrichton/rust/freebsd-libm, r=thestinger

Apparently we had forgotten to do this for freebsd, causing possible problems
on FreeBSD 10. The discussion in #12324 has some more details about how it's
missing.
syntax: add a some docs/clarification to the fields of ExpnInfo.
syntax: add a missing span rewrite in fold.

This was leaving Decls without the new spans; this is a minor change,
since literally nothing reads in the code base reads the span of a Decl
itself, always just its contents.
auto merge of #13135 : alexcrichton/rust/dox, r=alexcrichton

I touched up the documentation from @pcwalton found in #12952.
rustc: Relax restriction on privacy for fields

This is a necessary change in preparation for switching the defaults as part
of #8122.

RFC: 0004-private-fields